1. Field of the Invention
The present invention relates to an improved thermoresponsive, soft/hard, distal tip portion for any catheter that provides atraumatic contact with the lumen of a conduit. The distal tip portion is an improvement for many types of catheters used for both, the delivery and withdrawal of fluids and devices, especially by the trans-brachial approach. The applications include interventional guiding catheters, coronary catheters, drainage catheters, chemotherapy delivery catheters, and neuroradiology catheters, among others. The thermoresponsive distal tip portion can be used as a sheath tip for a sheath introducer for peds. Also, it can be used as a sheath tip for a trans-brachial or neuro procedure.
2. Description of the Prior Art
Catheters are thin flexible tubes, which are introduced into a vein or artery and guided to selected sites in the vascular system. Angiographic catheters are employed to inject contrast media into a vessel to visualize the shape, state, topography, functionality and other characteristics of the vessel for the purpose of diagnosing anatomic abnormalities of an organ and its conduits. Such catheters are used, for instance, to diagnose diseases of the heart and the circulatory system.
The guidance of a catheter within a tortuous vessel structure, such as a coronary artery and the arteries supplying the brain, often present difficult challenges. Efficient guidance of the distal portion of the catheter may be achieved by various means, including the use of a guidewire, essentially a long, slim and flexible wire or coil on which the catheter's lumen rides or slides to the desired location. An adjunct to the guidewire, various pre-shaped distal configurations have been widely used for such applications as entry into the coronary arteries from the aorta, or for entering the Circle of Willis within the brain. The thermoresponsive distal tip portion for a catheter of the present invention is directed toward improving the performance of both guidewires and catheters with pre-shaped distal portions. For example, the soft tip minimizes thrombus formation when scraping or damaging sensitive arterial walls during movement of the catheter within a blood vessel.
The introduction of a catheter into a vessel and its maneuvering within a vessel are less traumatic when the distal or leading portion of the catheter is soft at the time the catheter comes in contact with the vessel. A soft distal portion of the catheter made of a polymeric or rubbery material in the range of about 35-40 Shore D hardness is desirable. Nevertheless, the degree of softness may present a problem while the catheter's soft distal tip portion is passed or forced through a percutaneous introducer system including an introducer catheter having a hemostasis valve. The introducer facilitates the percutaneous insertion of the catheter by eliminating the need for a surgical cut-down to the vessel, and the hemostasis valve usually employs a membrane for the catheter to pass through without permitting blood to exit out of the vessel and from the body. When the distal portion is soft and rubbery, it may become severely deformed by the force needed for its insertion through the homeostasis valve. When the soft polymeric or rubbery distal portion demands a great deal of force to be passed through the introducer and hemostasis valve, the soft portion may be damaged, tom or even separated from the rest of the catheter. The excessive traction force or friction is the consequence of the soft rubbery interface with the percutaneous introducer housing, hemostasis valve and cannula. If the entire soft distal end or even a part of it were to detach due to excessive traction, then this may cause serious medical complications, even surgical intervention may become necessary during the catheterization procedure.
A variety of catheter and soft distal tip improvements have been made since the first human catheterization was performed by Forssmann in 1929. An example of such improvement is taught by the Horrigan et al. in U.S. Pat. No. 5,811,043 as well as others. Nevertheless, the prior art of soft distal ends or tips takes into consideration a virtual steady state softness of the distal end within a temperature range of 15 to 40° C. In effect, the soft distal tip portion of the catheter remains soft at both room temperature and body temperature. Certain materials employed for the distal tip portion become even softer at body temperature than at room temperature and lose strength as they become softer. This characteristic may pose a further problem upon completing the catheterization procedure and retrieving the catheter from the body through the percutaneous introducer system, as part of it may tear off and remain inside the vessel.
Other U.S. Patents of interest with respect to thermoresponsive materials are listed below:
U.S. Pat. No.Patentee5,957,966Schroeppel5,997,526Giba et al.6,001,078Reekers6,002,969Machek et al.